Method and apparatus for recording and reproducing sound



March 23, 1937. P. I oHN ET A1. '2,074,406

METHOD'AND APPARATUS FR RECORDING AND REPRODUGING SOUND Filed July 26,1953 2 Sheets-Sheet 1 fnnnnn'mnnnnn'nmmnnnml DUUUUUUEUUUU my. 3. f6 M @y0' I l' 47 D .'/5 A INVENTORS @LFO/V60 CORTELLH' ATTO RM March\23,n1937. P. LOHN ET AL METHOD AND APPARATUS FO'R RE CORDING AND REPRODUCINGSOUND 2 Sheets-Sheet 2 Filed July 26, 1935 M E sf www m62 E L wo? r an..Wr MP 7 an I ATTOR E S Patented Mal. 23, 1937` f f A 2,074,406

Peter New York, N. Y., and Alfonso CortellaiLeonia, N. J.

Application July 26, 1933, Serial No. 682,292

2 Claims.

'I'his invention relates to improvements in the recording andreproduction of sound and has particular reference to a method andapparatus for making and reproducing a sound record on a recordingmedium such, for example, as a lm employed in the motion picture art.vThe invention pertains more especially to the production of a motionpicture iilm which is capable of being employed in conjunction with 1oprojectors of the type used in the home and which will enable thesynchronous reproduction Vof sound with the picture on the film, but itwill be understood that the inventive concept embodied herein is not tobe construed as limited l5 to such use.

Various kinds of lms having sound records thereon have heretofore beenused amongvwhich are those in which the film is provided with aphotographic sound record. Such a film has been ioundquite effective inprojectors employed in motion picture theatres. But the necessity ofutilizing the expensive equipment, including photo-electric cells andassociated apparatus, makes its use with a home projector too expensiveand therefore impractical either when such equipment is installedoriginally in the machine or is provided as a separate unit forapplication to a projector theretofore' unequipped for the reproductionof sound. A,

Another previous proposal involves the formation of an ordinary hill anddale record groove cut in a surface of the lm. Such a recordnecessitates the use of a stylus which, if of a relativelysoft material,Wears downand must be frequently replaced, and which, if of a hardsubstance such as steel or the ,likefhasvan adverse effect upon therecord groove. In either instance, the reproduction of the sound ismaterially impaired and its quality therefore diminished.

A further prior suggestion, which has been practiced to some extent,resulted in forming the record groove in an edge ofthe film forengagement :by the stylus of a pick-.up device. Such.

practice has never, so far as known, been entirely successful inobtaining quiet reproduction, owing to the roughness of the edge of thelm as compared to the surfaces thereof, which roughness, in spite ofattempts to obliterate'the same by polishing said edge, has resulted inthe production of extraneous sounds. `Nor has such reproduction.approached perfection in its accuracy' due to the .tendency of-the lmto buckle by reason of the pressure of the stylus thereagainst. Inaccordance with the present invention, it

is proposed to eliminate the diiliculties encountered in known types ofsound recording films by the production of an improved recording mediumin which the sound record therein is ofl such nature that its engagementwith a recording stylus will result in an accurate reproduction,

without extraneous noises, of the sound to bereproduced. The presentmedium is also of such a character that the same can be produced at acost which will make feasible its use with home projection apparatus.

The invention furthercontemplates a sound record produced in a exiblestrip, as for example a photographic lm, by a relative vibratorymovement between said iilm and a cutting tool which will result in thelatter cuttinga record groove in one surface and an edge of said strip.The term trace as employed throughout this description is intended, inits broadest sense, to cover a recordin which either a continuous cut ora series of individual but correlated cuts combine to produce thedesired sound waves.

A still further feature of the invention resides in reproducing thesound record in a flexible strip by moving the latter past a pick-updevice in such a manner that the inherent tendency of the strip toassume a normal flat position is utilized to effect sufficient pressureofthe strip and its record against the stylus of said device tofaithfully reproduce the sound.

The inventive idea involved is, capable of receiving a variety ofexpressions, some of which,

`for purposes of illustration, are shown in the accompanying drawings,wherein:

Figure 1 is an enlarged fragmentary plan view l of a motion picture lmto which the sound record of the present invention has been applied.

Figure 2 is a 4greatly enlarged transverse section through the lm, thedotted lines indicating thev relative position of the stylus of apick-up device when engaged with the sound record.

Figure 3 is a diagrammatic elevation of one form of apparatus used forrecording sound upon the lm.

. Figure 4 isan enlarged elevation, partly in section, of the soundrecord-forming apparatus of Figure 3.

Figure 5 is a view similar to Figure 4 showing another form of recordingapparatus.

Figure 6 is an assembly view, in elevation, of a projection apparatus,and sound reproducing mechanism made in accordance with a presentinvention.

Figure '7 is an enlarged longitudinal section through a. part of thereproducing mechanism.

Figure 8 is a plan view of the mechanism shown in Figure 7, With thecasing thereof in section, and

Figure 9 is an enlarged transverse section substantially on the line 9-9of Figure 8.

The present invention is illustrated in its application to aphotographic lm such as used in motion picture projecting machines butit is to be expressly understood that the sound record involved hereinmay be applied to any other kind of flexible recording mediumwithoutdeparting from the spirit or scope of the invention. The lm IIJshown herein is of the usual type made of plasticized material includingthe united layers of celluloid II and sensitized emulsion l2 the formerof which is of the greater thickness. According to the present inventionthe record trace generally indicated by the numeral I3 is preferablyformed, by a cutting means later to be described, in the celluloidsurface II and a longitudinal edge of the lm. The trace consists ofminute series of cuts made in said surface and edge and these cutsextend transversely of the film body, and preferably diagonally thereofasclearly shown in Figure 1, although it is conceivable that they may beperpendicular to said edge. The cuts forming the record trace vary indepth and length in accordance with the frequency of the vibrationswhich are transmitted either to the lrn or to the cutting tool, as will'appear in the course'ot the description, but it is desirable, in orderto effect reproduction of high quality, that the depth of said cuts atno point shall be equal to the thickness of the film and preferably donot exceed the thickness of the celluloid layer II. Also, due to therelative position of the edge of the film and the cutting tool, thelength of the cut in the film surface will be substantially the same asthe greatest depth of the film, as shown in Figure 2. In no event,however, will the length of the cut be such that it will extend into thecentral area of the film which is occupied by the picture photographedupon the emulsion side I2. When the cuts of the trace are formeddiagonally, as shown in Figure 1, they preferably extend outwardly in adirection opposite that to the travel of the film as it is being movedpast and engaged with the stylus of a pick-up deviceso that said stylus,which may be of any desiredA hard material and of substantially the formshown in Figure 2, will easily and accurately .engage the undulations ofthe record trace with a constancy which will faithfully reproduce therecord. In Figure 1 several blank spaces have been shown between seriesof the cuts forming .the record trace. These blank spaces are actually apart of the complete sound record but represent silent intervals in saidrecord.` By reason of the -fact that the sound record is formed in theysmooth celluloidsurface of the film the engagement of the stylus withthe saidblank spaces will reduce to an absolute minimum any possibilityof scratching noises being createdlduring the said silent intervals.

In Figures 3 and 4 there is illustrated diagrammatically one Vform ofrecording apparatus.

The film IU, with its celluloid side I I uppermost is fed lbetweenrollers I4 to and through the armature I5 of a quick-actingelectromagnetic device I6 of any well-known construction capable ofresponding to high frequencies and accurately transmitting the same toits armature in order to vibrate the latter in accordance with suchfrequencies, there being a spring I5' connected to the armature to holdthe' latter in engagement home projection apparatus.

with the cutting tool I'I against the action of the device I6. Thecutting tool is preferably in the form of a disc knife, driven at thedesired speed by a flexible shaft I8, and is suitably suspended adjacentthe edge of the lm in which the sound record is to be made and the planeof said knife is preferably disposed diagonally to the direction oftravel of the film so that the cuts forming the record trace will bedisposed diagonally relative to the longitudinal edge of said film.Preferably, when the electromagnet I6 is deenergized the armature I5 isso positioned that the film is in contact with the cutting edge of thecutter I1 but as the armature is vibrated said film, as it is movedalong, will be likewise vibrated relative to the cutter and the desiredcuts made in the surface II and its longitudinal edge.

I y The apparatus shown in Figure 3 is employed when translating ortransferring a sound record from one lm to another and is especiallyadapted for making the sound record in asmall lm, such as the film II)which may be used.with small The master film I9 which is employed toform the sound record in the film I0 has a photographic sound recordtherein and is fed by series of rollers 20 between a projection unit anda photo-electric cell conventionally illustrated by the numerals 2l and22, respectively. The cell 22 is responsive to the sound record on thelm I9 and impulses are transmitted from said cell through the circuit 23connected to the electromagnet I6, there being a suitable amplifyingunit 2t interposed in said circuit between said magnet and thephoto-electric cell.

Instead of vibrating the film I0 into contact with the cutter I'I, asshown in Figures 3 and 4, the film I0 as illustrated in Figure 5, may bemoved through a stationary guide 25 and the cutter 26, constantlyrotated by the flexible shaft 2l, may be carried by the solenoid of theelectromagnetic device 29 which would be included-in the circuit 23 inthe same manner as the device I6. Thus the cutter 26 would be vibratedin response to the impulses transmitted thereto by the photo-electriccell and said cutter would constantly be moved into and out ofengagement with the surface I l of the lm and its edge to form therecord trace therein.

Figures 6 to 9 of the drawings illustrate an apparatus for reproducingthe sound record of the abov'e described film. In Figure 6 there isconventionally shown various instrumentalities which may be employed ina combined sound and motion picture apparatus especially suitable forhome use. The numeral 30 indicates a picture projection machine whichmay be of a well known construction. The sound reproducing unitgenerally indicated by the numeral 3l is designed so that it can be soldas a separate unit and coupled with a projection machine already in useand has associated therewith any well known loud speaker 32 electricallyconnected to a pick-up device 33 located within the casing of the unit3|. The film I0 having the record groove I3 therein is mounted upon areel 34 supported upon the exterior of the casing 3| and is fed fromsaid reel around an idler 35 and from thence into said casing with thecelluloid side of the iilm' containing the record groove uppermost. Asthe lm enters the casing 3| it is passed through what is commonly knownas a gate consisting of the horizontally spaced guide members 36 which,in this instance, are made arcuate in cross section as best shown inFigure 9. The purpose of this gate is to tension the portion of the lmlocated between the members of the gate and where the sound record |3thereof is being engaged by the stylus of the pick-up device. Inaccordance with 5 the present invention it is proposed to utilize thenatural tendency of the film to assume a flat condition after it hasbeen flexed in order to obtain the pressure sufficient to cause therecord in the film to properly engage the stylus of the pick-up 10device. To this end, there is provided an idler roller "31 journalled onthe shaft 38 extending between'the side walls of the casing 3| beneaththe lm I and in vertical alignment with the device 33.v The bearingsurface of the roller 31 engages 15 the lower or emulsion side of thefilm I0 and is curved transversely so that the lm l0 will be Afterleaving the `tension gate in its travel through the reproducing unit thelm is passed over the drive sprocket 39 and from thence successivelyunder and over the idlers 4l), 4| and 30 42, the latter being located onthe exterior of the casing 3|. From this point the film is led to theprojection machinev 30 and between the latter and said idler 42, saidfilm is twisted, as indicated at 43, so as to bring the emulsion side'thereofl 35 uppermost.

In order to secure absolute synchronism between the projection machine30 and the sound reproduction, the shaft of said machine is connected bya flexible shafting 44 to a shaft 45` extending transversely of andmounted in the casing 3|, said shaft carrying the drive sprocket 39.lA'pinion 46 on said shaft 45 meshes with a bevel gear 4-'l carried bythe drive shaft 48 operated by any suitable prime mover such as anelectric motor (not shown) What is claimed is:

1. Sound reproducing apparatus, comprising, in combination, a pick-updevice, a film having a sound record in one surface thereof, means tomove said lm and said device relative to each other with the stylus ofthe latter in engagewith said sound record, and means to bow said filmtransversely so that the surface thereof containing the sound recordwill be in the convex arc of curvature of the lm.

2. Sound reproducing apparatus, comprising, in combination, a pick-updevice, a lm having a vsound record in one edge of one surface thereof,

means to move said lm and said device relative to each other with thestylus of the latter in engagement with theedge of said film containingsaid soundrecord, an arcuate guide through which said lm is moved, and aroller having a transversely curved surface, contacting only the medialportion of the surface of said film opposite to that containing thesound record so as to bow said lm.

PETER LoHN.

AriFoNso CORTELLA.

